30 Pedersen RA 18 thin and thick walled?

In HWS vol. 1 p. 67 they talk about cases with thin side-wall construction and with thick
side-wall construction. All have different head stamps except RA 18 that is used in both
thin and thick walled cases. Is there a known weight difference or some other way to tell the two apart?
Thanks , Bob

To me it looks like the RA, RA H 18, & RA H 19 have the thin side-wall construction.

 The RA 19 and F A 20 have the thicker side-wall. 

BUT, some of those have 80 and some 90 grain bullets,
and also some are .01 shorter which would be lighter.
And RA and F A cases could possibly vary.

 So I don't know if one could tell the side-wall by weight. 

Maybe someone else will have a way.
(I don 't have a F A, and trying not to get the scale out!)

cztrouba - I had never investigated this before, as the .30 Pedersen is peripheral to my auto pistol cartridge collection, kept only because it led to the 7.65 French Long and the designation for the Pedersen Device was “Pistol” to conceal the purpose of the development.

I just weighed all of the “short bullet” variations of .30 Pedersen in my collection - seven and came up with the following:

REM-UMC 32 ACP - 128.7 grains (Prototype load)
REM-UMC 9mm BS - 128.9 grains (Prototype Load)
RA H 18 - 129.2 grains (Hoboken Plant)
RA H 18 - 129.3 grains (Hoboken Plant)
RA 18 - 128.7 grains
RA - 133.1 grains (no date on headstamp)
RA 18 - 133.1 grains

I cannot, in good conscience, say with positivity that the different weights are based on the thin and thick side-wall construction. I can say that the Prototype Loads would be of the lighter construction, as would be the Hoboken loads, since they never made the thick-side-wall case. All four of those loads in my collection are in the approximately 129 grain weight level. One of my RA 18 loads is also at that level, while the remaining RA 18 cartridge is at the approximately 133 grain level. Coincidental? Not likely. Roughly 4 grains difference in weight between the thin-wall and thick-wall cases would seem reasonable. Unfortunately, I have no duplicates (never bothered with hardly any) to have sectioned, so again, I am hesitant to draw a positive conclusion.

However, it does appear that you can differentiate between the two loads based on total cartridge weights (of course, we exclude the later “long bullet” rounds-90 grain bullets rather than the original 80 grain version).

There are also short cases and long cases, differing only in case length by 0.175 inches. I separated my rounds accordingly, but with no confidence, as my shaky 80-year old hands and poor close vision preclude me getting an accurate measurement that small, even with my good quality, digital caliper. I did it simply by eye, lining up all the cartridges, and there did seem to be two distinct lengths. Again, no confidence in the accuracy of that form of measuring!!! :-( Because of that, and the fact that overall cartridge weights were not measurably affected, I did not bother to show “short case” and “long case” in the table of weights above.

John Moss

Thanks Dan And John
The only two I have on hand at this time are RA H 18, 128.8 grains and RA H 19, 130.5 grains and they both should be thin wall. John, Your weight difference of about 3 to 4 grains is about what I expected but the RA (no date) 133.1 grains puzzles me as it should be a thin wall. The RA 18 should be the only one made in both thin and thick wall cases.
I should have a few more in a week or two to weigh and I will post them when they come.
I also have a friend with a Pedersen Divice and I’ll check with him to see if he has any empty cases I can weigh.
Thanks, Bob

Your RA H 19 headstamp is nice. I do not have that date, so hard for me to comment on it. Things other than the case-wall thickness could influence the weight, since your round at 130.5 grains is closer to what we are assuming is the "thin wall weight) than it is to those we believe to be “thick wall.” I agree with your confusion over the “RA” undated round. One would think this would have been the first round other than the two REM-UMC commercial headstamps, used as a subterfuge. However, HWS Vol. 1, also on page 67, indicates “…and a January 6, 1919, revision added year of case manufacture to headstamp.” Yet, we have “18”-dated cartridges! I simply don’t know of the actual act of marking the date on headstamps pre-dated 1919, or not. We had a saying in the Army, “ignore the order and wait for the change.” This situation seems to be “make the change, and then issue a revision order to cover it.”

All I can do is accurately weigh the cases (RCBS electronic digital scale) and report the weights. I rechecked the “RA” headstamp round, and the total cartridge weight oriinally quoted was correct.

The only empty case (primed, with correct but separate bullet), is my F A 20 .30 Pedersen, and weighing that case would not, in my opinion, answer any questions, since it is later production than the others and from a different factory.

John Moss

I have two primed empty F A 20 headstamped examples.

One weighs 52.1 grains & is 19.75mm long w/ case wall at the mouth 0.37mm
One weighs 51.7 grains & is 19.96mm long w/ case wall at the mouth 0.42mm

A loaded F A 20 example weighs 135.5 grains & the case length is 19.73mm

Dillon D-Terminator electronic scale used.

Interesting. That makes an F A 20 round the heaviest, but only by enough that it could be accounted for even by use of a different powder to produce the same velocities as the Remington production. Or, the case itself could be a little heavier. I had no Remington empty cases to weigh.

Just for the record, my F A 20 empty primed case weighs 51.4 grains. Length is 19.75 mm. Case wall at mouth is 0.44 mm.0.37 to 0.38", depending on where measured.

John Moss

Thanks Pete
HWS vol 1 page 67 states “A 1919 revision shortened case by 0.010 in. A slight modification of this case with a stronger head was made at Frankford Arsenal during the 1919-1921 period.”
Like John .010 is hard for me to measure but .010 off the case neck should not weigh too much.
The stronger head might account for some of the weight difference.

PS As a test I decided to trim a case .010 and see how much that weighed.
I did not want to cut up a Pedersen case so I used a 30 carbine case…010 off of the neck = just over .1 grains and not enough to figure in total weight in my thinking but a stronger head might very well add more weight.

I have received weights on 22 different RA 18 cartridges and have divided them into 2 groups.
group #1 --15 cartridges 127.8gr to 129.7gr = + or - 1.9gr
group #2 – 7 cartridges 130.9 to 133.1 = + or - 2.2gr
There is a gap between the two of 1.2gr with no cartridges found.
I’m not sure but this must be related to the case thickness.
If I were in Saint Louis tomorrow like I had planed I would look for a few to take apart to weigh and measure the cases alone. Well it’s only a year to SLICS and if I’m still here I will be there looking for more treasures.

I’m not sure at all, that cases made by RA had the thick & thin walled cases I was under the impression only FA did that?

Also to my mind & I may be wrong, the brass, powder, lead or jacket material used during the length of manufacture time could contribute these weight differences? 133.1 gr - 127.8 gr = 5.3 gr

Another factor, if as you say you “received weights”, which sounds as if folks weighed theirs & then reported to you? The various scales being used could also contribute to a false or uncertain conclusion.

A friend who has a rifle barrel shop in town, has said to me the various digital calibers being used / sold are not all accurate to .001inch. My point being measuring is dependent on the tool used, and unless calibrated the results may be perhaps incorrect.

Hello Pete
I am going on what is said in “History of Modern U.S. Military Small Arms Ammunition” volume 1 page 67 by Hackley, Woodin and Scranton. They list cases made in thick and thin walled and only RA 18 is listed as using both. FA cases are listed as thick walled only. I agree that weighing without calibrating could cause errors but at this time that is out of my control and I have to count on people sending me accurate weights. Most people have sent the type scale they used (Lyman, Dillon, RCBS,and Lee) and I would think the error between major brands would be in tenths of grains and not full grains.
I think the only way I will know for sure is to take a few apart and measure them.
Thanks again

OK, if you note above the two examples I measured wall-thickness are FA & why I was confused. I was unaware of what constituted a thin wall but saw a differene in these two.

Understand your needs vs various inputs.

Good luck in your search
For more input I have 2@ RA 18 examples. The loaded example weighs 131.0 gr on my Dillon D-Terminator. And a dummy with a struck primer, and two 2.85mm / 0.1125" diameter lower middle case holes (drilled through) weighing 128.0 gr.

I now have weights on about 60 RA 18 cases and they range in weight from 128.1 gr. to 133.2 gr. I have taken apart 2 in the lighter weight group and the case wall thickness is .0181" and .0188" (averaging 3 measurements taken on each case near the head) 1 case in the heavier group measures .0263" I’M not yet sure where the dividing line is between thick and thin walled cases. According to HWS the Bridgeport plant made 1,500,000 thin walled cases and 4,500,000 thick walled cases. All 3 of the thin cases I have are primed with nickel primers and all others when specified (about 45) are copper primed. HWS says only RA 18 cases have been seen with both nickel and copper primers.